The insects commonly known as ladybugs (or ladybirds, in the UK and other English-speaking nations) include a number of species from the Coccinellidae family. Ladybugs are the subject of nursery rhymes and are considered a good luck symbol by many. For example, the seven-spot ladybird, the most common species in Europe, is said to represent the seven joys and seven sorrows. The ladybug is often considered a symbol of the Virgin Mary in Christian culture.
Ladybugs are not true bugs, but rather a group of some 6,000 small beetles that share a similarity in markings—orange or scarlet shells with black spots. These insects are more accurately called lady beetles. Most of the species are considered beneficial insects, since they feed on agricultural pests such as aphids and scale insects. Some species are natural predators of very serious pests such as the European corn borer. In fact, the most prevalent North American ladybug, the Asian ladybug, (Harmonia axyridis), was introduced from Asia in 1916 to combat aphids. The USDA released the Asian lady beetles in Georgia, South Carolina, Louisiana, Mississippi, California, Washington, Pennsylvania, Connecticut, and Maryland, and the beetle has since then migrated throughout most of the United States. Along with this intentional introduction, it is likely the beetles reached the U.S. on freighters, adding to its presence throughout the country.
The Asian ladybug is a predator of a number of pest insects, especially aphids, but it has become a problem because it has overtaken native species. It is also this species of ladybug that may occasionally bite the hand that lovingly thinks it is playing with one of the harmless native ladybugs.
Distinguishing Native Ladybugs from Asian Ladybugs
At a quick glance, it can be hard to tell the difference between the Asian ladybug and the native ladybugs, partly because the color of the Asian species can vary from light tan or orange to bright red, making them almost identical to some of the native species. But if you look closely, you will see the Asian ladybug has a white marking behind its head in the openings of what looks like a black M. Some also have dark black spots, but on others, the spots are very light or nonexistent.
Asian Lady Beetle Infestations
Since their purposeful introduction, some not-so-beneficial qualities of Asian ladybugs have become apparent. Like boxelder bugs and stink bugs, Asian lady beetles will crawl into cracks and crevices of the home on the eaves, siding, or even the foundation to overwinter between the walls. They can then come into the house through the winter seeking its warmth.
Once inside, the insects can crawl or fly around rooms and land on windows, walls, and furniture. Like other ladybugs, the Asian variety secretes a yellowish, smelly fluid if disturbed, which can stain walls, furniture, and fabrics.
Asian lady beetles are typically somewhat more aggressive than native varieties and may bite if they land on the skin. Though the bite is not very painful, some people can have allergic reactions, ranging from eye problems like conjunctivitis ("pink eye") to hay fever, cough, asthma, or hives. Reactions can be triggered by touching the lady beetles then touching your eyes, or just by being around a large or lengthy infestation of the insects.
Although the Asian lady beetles do help rid gardens of plant pests, they are becoming a problem in vineyards, where they can end up being "collected" along with the grapes, affecting the taste of the wine.
Controlling Asian Lady Beetles
The best way to control Asian lady beetles in your home is through pest-proofing measures to keep them from entering. These include sealing any cracks around windows, doors, utility wires and pipes, and vents, as well as in the siding, eaves, and foundation. It also is important to be sure that all doors and windows are tightly fitted, and that screens are not torn or ripped. If the ladybugs do get in your home, they can be vacuumed or captured on sticky tape. To avoid staining and odor, do not try to swat or squash the bugs.
Gardeners seeking to introduce beneficial insects should take care not to purchase and distribute ladybugs from commercial sources. These commercial ladybugs may be the Asian variety. While some "safe" species are sold, including Hippodamia convergens (convergent ladybug), Adalia bipuntata (red ladybug), and Coleomegilla maculata (spotted ladybug), these insects may have been harvested in the wild to offer for sale, which is a questionable practice.
A better strategy is to practice non-chemical gardening methods that encourage native ladybug species to visit your garden.